This invention relates to the lining of landfill sites for receiving waste, and more particularly, but not exclusively, to provision of a support structure for a flexible impervious lining intended to contain the waste material and to prevent elements of that material from draining into or being leeched from the waste into the subsoil and water table.
Spent or disused quarries and other excavations are commonly used for tipping domestic and other waste. The sheer variety of material contained in such waste virtually ensures the presence of potentially environmentally damaging materials. There has for some years been increasing concern to prevent such potentially damaging materials either from draining from the tipped waste into the subsoil and further, or being leeched from the waste by rainfall to the same effect. Quarry and other excavation sites may or may not be in substantially impervious materials, but the tendency now of authorities responsible for environmental protection is not to rely on that and, whether the proposed landfill site is in impervious material or not, to require provision of an impervious lining at least along the base and up the side walls of tipped sites, and in some cases for that lining to be completed by a sealed impervious cap so as totally to enclose the tipped material.
A variety of methods for lining a tipping site have been proposed. It is all but essential now for such lining to comprise a continuous flexible impervious lining produced by welding or otherwise affixing together discrete sheets of the lining material. Given the irregularity of the walls and base of most landfill sites, it is generally not feasible simply to lay a flexible sheet or membrane in place and various methods have been proposed for provision of a stable substrate eg constructed out from the walls of a disused quarry, against which the flexible membrane can sit and be supported without concern over breach of the flexible material by interaction with it by the quarry face and/or the tipped waste. There are such methods which involve essentially building a fresh wall to the quarry for example using gabions containing rocks or the like, or by use of a rigid metal framework to which are attached sheets of expanded metal. The former has a number of disadvantages not least of which that it involves substantial incursion into the tipping volume available. The latter involves initial construction of an extensive and robust framework around the quarry wall and moreover can suffer problems with cutting of the flexible liner sheet by the proud edges of the slits of the expanded metal sheet.
It is an object of the present invention to provide a simpler, more effective and cheaper support construction for a flexible impervious lining of a landfill or tipping site such as a quarry.
It will be appreciated in this specification that references to quarries are not, unless the context is to the contrary, intended to be restricted to quarry sites themselves and can refer equally to other excavated tipping sites or even naturally occurring tipping sites.